Momo Umezono is a wealthy teenage girl whose family's financial status parallels Kyle Matsutake's. She possesses curly blonde hair styled with a bow and black eyes, frequently adorned in elegant attire reflecting her affluent background. Her primary motivation stems from her romantic interest in Kyle, fueling her rivalry with the series' protagonist, Katie Minami. Observing Kyle's persistent attentiveness toward Katie, Momo develops envy and consistently mocks Katie by calling her "oba-san" (auntie), perceiving her as an obstacle to Kyle's affections.

She enters the main storyline in Episode 68, becoming the human partner to the fairy Yamane, a female ninja muglox who admires Yatch and wields a bird whistle as her magical instrument. This partnership integrates her into the narrative's supernatural elements. Momo employs Yamane's abilities in schemes designed to disrupt Katie and Kyle's interactions, though these plans typically fail due to comedic mishaps or interventions by other characters.

Momo is accompanied by her butler, Hoshino, who serves as a direct counterpart to Kyle's butler, Hirai. While their roles position them as professional rivals, the narrative occasionally hints at an underlying mutual respect or softer dynamic between Hoshino and Hirai. Her character maintains a consistent focus throughout her appearances, depicting no significant evolution or resolution regarding her romantic pursuits toward Kyle or her rivalry with Katie. Her role primarily functions as a recurring source of comedic tension centered on unrequited affection and social competition.